Ryozo Furukawa

High-power operation of 830-nm AlGaAs laser diodes

We have developed a high‐power, semicylindrical‐shaped waveguide inner stripe laser diode (SCILD) using a current confinement structure. The structure is optimized for high‐power operation without catastrophic optical damage (COD) which limits the maximum available optical power. We confirm that the optical electric field shape in the LD waveguide layer obtained from our analysis coincides with the micrograph of the COD on the device facet. The SCILD is emitted in the fundamental transverse mode up to 190 mW. The full beam angles between the half‐power points were 10° and 30° in the directions parallel and perpendicular to the junction plane, respectively. The characteristic temperature of the threshold current was 152 K.

Optical devices from AlGaAs-GaAs HBTs heavily doped with amphoteric Si

A new optoelectronic multifunctional device, having triple function of light emission, detection and amplification have been developed and some preliminary integrated circuits are demonstrated. The devices consist of N-p-n or N-P-n AlGaAs-GaAs HBT utilizing amphoteric Si heavily-doped GaAs or AlGaAs p-type base layer. Maximum current gain of 3600, and light output power of about 0.17 /spl mu/W with 100 /spl mu/A base current (I/sub b/) in transistor mode operation and of about 10 /spl mu/W with I/sub b/=40 mA in diode mode operation are obtained. The optical emission wavelengths in both are about 0.85-0.86 /spl mu/m. Optical gain of about 130 was obtained near the 0.86 /spl mu/m wavelength as a detection transistor. Spectrum matching between emission and detection wavelength range is achieved. Some monolithic integrated circuits constituted of the transistors are proposed and demonstrated successfully. The relationship between current gain and radiative quantum efficiency at the transistor operation is also discussed. >

Supermode control and phase front measurements of phase‐locked offset‐coupled laser arrays with a large optical waveguide structure

Phase‐locked array lasers with large optical waveguide structures are demonstrated. The refractive index guides of each laser are evanescently coupled with and without offset‐coupling structure. An evanescently coupled three‐element laser array without offset coupling regions emits up to 200 mW and an offset‐coupled laser array with a 4/5 element emits up to 150 mW under pulsed operation. Both laser arrays emit with all elements in‐phase locked and produce a single narrow far‐field lobe. The full widths at half maximum of the three‐element and 4/5‐element laser arrays are 5° and 2.5°, respectively. In phase measurements of the lobe of the 4/5‐element laser array, we find that the root‐mean‐square aberration is less than 0.11λ under pulsed operation. This phase aberration is constant with varying power from 75 to 150 mW.

Low-Phase-Aberration Output of 830 nm AlGaAs Offset-Coupled Laser Arrays

Phase-locked lasers with refractive-index waveguides have been developed. The elemental stripes of the laser are evanescently and offset coupled. A fundamental supermode operation in the 2/3-element laser arrays is achieved. The phase aberration is less than λ/14 (λ=830 nm). The output power of the laser array increases almost linearly up to 200 mW with an external differential slope efficiency of 0.75 W/A.

Phase front measurements of AlGaAs 830 nm phase‐locked lasers with a real‐refractive‐index waveguide

A phase‐locked laser array with refractive‐index waveguides and emitting a low phase‐aberration beam is described. A fundamental supermode operation of an evanescent‐coupled three‐element laser array which emits up to 200 mW in a single diffraction‐limited beam is achieved. The full beam angle at the half‐power point is 3.2° in the direction of parallel to the p‐n junction. This phase aberration is less than λ/14 from 50 to 150 mW. The extremely low phase aberration (0.022λ) is measured at 50 mW.